A typical example of an exposure apparatus used to manufacture a device, such as a semiconductor device, includes a step and repeat exposure apparatus (stepper), which sequentially exposes the pattern of a master (reticle or mask) onto a plurality of exposure regions on a substrate (e.g., a wafer or glass substrate) through a projection optical system while stepping the substrate, and a step and scan type exposure apparatus (scanner), which repeats stepping and scanning exposure to repeat exposures and transfer onto the plurality of regions on a substrate. In particular, the step and scan type exposure apparatus uses exposure light after limiting it with a slit to a component comparatively close to the optical axis of a projection optical system, so that it can expose a micropattern at a higher accuracy with a wider angle of view. Some exposure apparatuses draw a pattern on a substrate with an electrosensitive particle beam, such as an electron beam or ion beam, in place of light.
Each of the exposure apparatuses has a stage device or driving apparatus (wafer stage or reticle stage), which aligns a wafer or reticle by moving it at high speed. In such an exposure apparatus, when the stage is driven, a reaction force of an inertia force accompanying acceleration and deceleration is generated. When the reaction force is transmitted to a stage surface plate on which the stage is mounted, the stage surface may swing or vibrate. Such vibration induces characteristic vibration of the mechanism system of the exposure apparatus to generate high-frequency vibration, which may interfere with faster, higher-accuracy alignment.
To solve the problems relating to the reaction force, several proposals have been made. For example, according to the apparatus described in Japanese Patent Laid-Open No. 5-77126, the stator of a linear motor, which drives a stage, is supported on the floor independently of a stage surface plate, so that swing of the stage surface plate caused by the reaction force is prevented. According to the apparatus described in Japanese Patent Laid-Open No. 5-121204, a machine frame supports a wafer stage and a projection lens. An actuator, which generates a force in the horizontal direction, applies to the machine frame a compensating force equivalent to a reaction force accompanying the drive of the stage. Swing of the apparatus caused by the reaction force is thus decreased.
In any of the conventional examples described above, although the swing of the stage apparatus itself can be decreased, the reaction force accompanying the drive of the stage is transmitted to the floor directly or through a member that can be substantially regarded as being integral with the floor. This may oscillate the floor and vibrate devices set around the exposure apparatus, thus, adversely affecting the peripheral devices. Usually, the floor where the exposure apparatus is installed has a natural frequency of about 20 Hz to about 40 Hz. As the exposure apparatus is operated, when the characteristic vibration of the floor is induced, it adversely largely affects the peripheral devices.
Recently, as the processing speed (throughput) increases, the stage acceleration increases more and more. For example, in a step and scan type exposure apparatus, the maximum acceleration of the stage reaches a gravitational force as high as 4 G in the reticle stage and a gravitational force of 1 G in the wafer stage. As the reticle or substrate increases in size, the stage mass also increases. Therefore, the driving force defined by <mass of a moving object>×<acceleration> becomes very large, and its reaction force is enormous. As the reaction force increases in this manner, oscillation of the floor for installation caused by the reaction force has become a non-negligible issue.
The size of the apparatus also increases largely, and in a manufacturing factory where many manufacturing apparatuses are installed, an increase in an area occupied by the apparatuses is becoming an apparent issue. More specifically, when the vibration transmitted from one apparatus to the floor is large, to prevent the other apparatuses from being influenced by the vibration, the distances among the apparatuses must be increased, and finally, the area actually occupied by the respective apparatuses increases.
Japanese Patent Laid-Open No. 2003-318082 discloses, in a driving apparatus which drives an object by a linear motor, use of the stator of the linear motor as a reaction force counter. According to the driving apparatus described in this document, when an object which stays still at the first position is to be moved to the second position and to be set still, the linear motor is controlled so that the object moves along a straight line connecting the first and second positions, to cancel a moment reaction force accompanying acceleration and deceleration of the object.
According to the technique described in Japanese Patent Laid-Open No. 2003-318082, the wafer stage must be moved along a straight line. In the step & scan type exposure apparatus, assume that the entire moving path of a wafer stage to sequentially expose a plurality of exposure regions S is formed of straight lines, as shown in FIG. 5. The wafer stage must be stopped at the terminal point of each straight line. This can interfere with an increase in throughput. In view of this, a process to sequentially expose the plurality of exposure regions S while continuously driving the wafer stage along a smooth curved line, as exemplified in FIG. 6, is sought.
To continuously move the wafer stage along the smooth curved lines, moderation of the limit for a Y-direction (X-direction) driving pattern by an X-direction (Y-direction) driving pattern (driving profile) is sought.
The present invention has been made on the basis of the recognition of the above problems, and has as its object to provide a technique that can cancel a reaction force accompanying drive of an object while moderating a limit for a driving pattern to drive the object in X and Y directions.
According to one aspect of the present invention, there is provided a driving apparatus, for moving an object, comprising a first actuator which drives the object in X and Y directions, a second actuator which drives a reaction force counter, which receives a reaction force generated when the first actuator drives the object, and a controller which controls the second actuator on the basis of X- and Y-direction positions of the object so as to cancel, by the second actuator, the reaction force to be received by the reaction force counter when the object is driven by the first actuator.
According to a preferred embodiment of the present invention, for example, the controller calculates X- and Y-direction accelerations of the object on the basis of the X- and Y-direction positions of the object, and controls the second actuator on the basis of the X- and Y-direction positions of the object and the X- and Y-direction accelerations of the object. Alternatively, the driving apparatus can further comprise an acceleration sensor, which detects X- and Y-direction accelerations of the object. The controller can control the second actuator on the basis of the X- and Y-direction accelerations of the object from the acceleration sensor and the X- and Y-direction positions of the object.
According to a preferred embodiment of the present invention, for example, the controller controls the second actuator so as to cancel, by the second actuator, X- and Y-direction reaction forces and a moment reaction force, which are to be received by the reaction force counter when the object is driven by the first actuator.
According to a preferred embodiment of the present invention, for example, the controller calculates X- and Y-direction reaction forces and a moment reaction force, which are to be received by the reaction force counter when the object is driven by the first actuator, and generates a profile to drive the reaction force counter on the basis of the X- and Y-direction reaction forces and the moment reaction force.
According to a preferred embodiment of the present invention, for example, the controller calculates the X- and Y-direction reaction forces Fx and Fy to be received by the reaction force counter and the moment reaction force Fr in accordance with:Fx=m·AccX Fy=m·AccY, andFr=y·Fx−x·Fy=m(y·AccX−x·AccY)where m, x, and y are a weight, X-direction position, and Y-direction position, respectively, of the object, and AccX and AccY are X- and Y-direction accelerations, respectively. The controller generates a profile to drive the reaction force counter such that Σ(FMx)=−Fx, Σ(FMy)=−Fy, and Σ(FMr)+−Fr are established, such that Σ(FMx) and Σ(FMy) are sums of X- and Y-direction thrusts, respectively, of the second actuator, and Σ(FMr) is a sum of moment thrusts. For example, the profile can comprise a profile that provides a thrust command value.
According to a preferred embodiment of the present invention, for example, the controller generates a profile to drive the second actuator such that Σ(M(i)·AccMX(i))=−Fx, Σ(M(i)·AccMY(i))=−Fy, and Σ(J(i)·AccMJ(i))=Fr are established, where (M(i)) is a weight of each of a plurality of reaction counters which receive the reaction force generated when the first actuator drives the object, AccMX(i) and AccMY(i) are, respectively, X- and Y-direction acceleration of each of the plurality of reaction force counters, and J(i) and AccMJ(i) are, respectively, a moment of inertia and an angular acceleration of each of the plurality of reaction force counters. For example, the profile can comprise a profile that provides an acceleration command value. For example, the controller can convert the acceleration command value into a speed command value and control the second actuator with the speed command value, or convert the acceleration command value into a position command value and control the second actuator with the position command value.
According to a preferred embodiment of the present invention, the reaction force counter can include a stator of the first actuator.
According to a preferred embodiment of the present invention, for example, the controller controls the second actuator to gradually decelerate the reaction force counter when a speed of the reaction force counter is not zero while a speed of the object is zero.
According to the second aspect of the present invention, there is provided an exposure apparatus, which has a chuck and transfers or draws a pattern onto a substrate chucked on the chuck, and in which the chuck can be driven by the driving apparatus described above.
According to the third aspect of the present invention, there is provided a device manufacturing method of manufacturing a device by using an exposure apparatus described above.
According to the present invention, for example, a reaction force accompanying drive of an object can be canceled while moderating the limit for a driving pattern to drive the object in the X and Y directions.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.